1. Field of the Invention
This invention is a catheter which includes an inflatable balloon fabricated from fluoropolymer resins. The catheter is useful in the fields of cardiovascular medicine, photodynamic therapy, cancer treatment, benign prostatic hypertrophy, neurovascular medicine, diagnostic medicine and other fields which require the use of a balloon catheter.
2. Prior Art
Percutaneous Transluminal Coronary Angioplasty (PTCA) is performed more than 400,000 times per year in the United States alone to treat the disease which is the leading cause of death, cardiovascular disease. In addition to PTCA, more than 250,000 Percutaneous Transluminal Angioplasties (PTA) are performed on the peripheral vasculature, again per year in the U.S. A treatment for cancer, the second leading killer in the U.S. (over 500,000 deaths per year), includes Photodynamic Therapy (PDT) of the gastrointestinal tract, urologic tract, pulmonary tree, and neurologic system. Photoatherolytic (PAL) Therapy has shown some early promise for the treatment of atherosclerosis and restenosis, and has been proposed for the Photoinhibition Therapy for Hyperplasia (PITH). Treatments of such widespread maladies such as Benign Prostatic Hypertrophy (BPH) and occlusive cancer of the esophagus include balloon dilatation, Interstitial Laser Photocoagulation (ILP), Laser-Induced Hyperthermia (LIH),Ultrasound Induced Hyperthermia, and Radio-Frequency Hyperthermia (RFH). The unifying parameter among the treatments for all of the above diseases is the use of a balloon catheter. The utility of the balloon catheter varies from dilatation to partial occlusion to total occlusion to short and long term patency (perfusion balloon) to local drug delivery to local device deployment to heat delivery to light delivery to various diagnostic applications to imaging to positioning to on line thermal, optical, or pharmacology dosimetry.
Angioplasty balloon catheters such as that described by Gruntzig, et at, in U.S. Pat. No. 4,195,637 and other prior art catheters adapted for the myriad of applications and utilities listed above are commonly fabricated from polyurethane, polyethylene, polyethylene terephthalate, polyethylene blends, polyolefin blends, nylon, polyamide, silicone, latex, etc. Materials such as these exhibit different qualities such as strength, biocompatability, compliance, and manufacturability, which are required for various medical procedures. As newer medical modalities are tested and proven, new demands are place on the qualities of the treatment balloon catheter device, such as optical clarity and thermal stability. Many of the materials stated above have a plurality of the requirements, but none have all, both old and new, requirements.
In cardiovascular medicine, balloon catheters are used for angioplasty (U.S. Pat. No. 4,323,071 Simpson), both in the coronary arteries and the peripheral vasculature which includes arteries of the arms, legs, renal system, and the cerebral arteries. Balloon catheters s are also used for photo-medicine in the treatment of cardiovascular disease (CVD) in procedures such as Photodynamic Therapy (PDT), Photoatherolytic Therapy, Photochemical Therapy, and Photo-Welding, either photothermal or photochemical, of an anastomosis (U.S. Pat. No. 5,169,395 to Narciso, Jr.). Balloons are also used for atherectomy/atherotomy for positioning and occlusion while they are also used in the deployment of various types of stents. Treatments for CVD which require balloon catheters outside of the treatment of atherosclerosis and restenosis include valvuloplasty and various electrophysiology procedures.
Cancer, the second leading cause of death in the U.S., can also be treated with procedures requiring balloon catheters. PDT is a very promising modality for this application (U.S. Pat. No. 4,932,934 Dougherty). PDT will compete directly with present laser therapies such as photocoagulation or ablative therapies to treat obstructive cancers. Another treatment being investigated is the use of localized heating (Hyperthermia) to selectively neerose cancer cells. The heat can be produced with a light source such as a laser or a non-light source such as a radio-frequency (RF) source, a microwave source, or an ultrasonic source.
Benign Prostatic Hypertrophy (BPH) is a non-cancerous hyperproliferative disease which invades the prostate of 80% of men by the time they reach the age of 80 years old. Various procedures are available for the treatment of BPH which include Hyperthermia (laser, RF, microwave, ultrasound), PDT, balloon dilation surgery and ablative procedures; all having varying success rates.
The forgoing materials have been successfully employed for catheters for many years. As mentioned above, new procedures such as transluminal hyperthermia require a balloon material which is transparent to the wavelengths of light employed for inducing hyperthermia and able to withstand high temperatures. In transluminal hyperthermia, a catheter which incorporates a balloon is inserted into a body lumen. The balloon, located near the distal tip, is inflated. A light diffuser tip within the catheter directs light from an external source through the wall of the balloon to penetrate the surrounding tissue. Currently employed elastomers for balloon fabrication are unable to withstand high temperature generated during such applications.
Additionally, when a catheter is stored for a long time with a balloon in a collapsed position, the elastomer comprising the balloon may stick to itself making inflation difficult. It is particularly desirable to provide a catheter having an inflatable balloon which employs a wall material which does not stick to itself. TEFLON.RTM. brand of fluoropolymer resins, which is not currently used as a wall material in such catheter balloons, has the desirable properties of high thermal stability, light transparency and a non-blocking (non-sticky) surface.
Teflon.RTM. is a DuPont registered trademark for a family of fluoropolymer resins. This family of fluoropolymers include: polytetrafluoroethylene (fluoropolymer), fluorinated ethylene-propylene (FEP), perfluoroalkoxy (PFA), and ethylene tetrafluoroethylene (ETFE). TEFLON.RTM. is characterized by its' extended thermal properties, resistance to virtually all chemicals, low coefficient of friction, lubriciousness, and relative clarity. Both FEP and PFA are melt-extrudable resins with the clarity required for optical applications and extended thermal characteristics inherent in all forms of TEFLON.RTM. brand of fluoropolymer resin. Both exhibit tensile strengths in the range of 4,000 psi with ultimate elongation percentage of 300-500 and a coefficient of friction in the range of 0.20-0.25. The flexural modulous is 95-105.times.10 psi and the continuous operating temperature is 204 degrees C. for FEP and over 260 degrees C. for PFA. The melting point for FEP is 253-282 degrees C. and 302-310 degrees C. for PFA. These properties make FEP and PFA excellent materials for fabricating a high temperature, chemical resistant, strong, optically clear, compliant easily manufactured balloon.
The greatest need for all of the applications previously listed is the ability of the walls of the balloon portion of the balloon catheter to withstand high thermal conditions. Regardless of the heating source (i.e. laser, arc lamp, LED, RF, microwave, or ultrasound), the device must not fail. Medical light and heat treatments require a dependable thermally stable balloon device. A balloon catheter meeting these requirements is described below.